This disclosure relates to gas turbine engine airfoils. More particularly the disclosure relates to airfoil gap/chord ratio in, for example, a gas turbine engine compressor or fan section.
A turbine engine such as a gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustor section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section. The compressor section typically includes at least low and high pressure compressors, and the turbine section includes at least low and high pressure turbines.
Direct drive gas turbine engines include a fan section that is driven directly by one of the turbine shafts. Rotor blades in the fan section and a low pressure compressor of the compressor section of direct drive engines rotate in the same direction.
Gas turbine engines have been proposed in which a geared architecture is arranged between the fan section and at least some turbines in the turbine section. The geared architecture enables the associated compressor of the compressor section to be driven at much higher rotational speeds, improving overall efficiency of the engine. The propulsive efficiency of a gas turbine engine depends on many different factors, such as the design of the engine and the resulting performance debits on the fan that propels the engine and the compressor section downstream from the fan. Physical interaction between the fan and the air causes downstream turbulence and further losses. Although some basic principles behind such losses are understood, identifying and changing appropriate design factors to reduce such losses for a given engine architecture has proven to be a complex and elusive task.
Similarly, the fan section can also be a significant noise source, as noise is produced by fluid dynamic interaction between the fan blades and the incoming air stream. Some fan blade arrangements have channels that converge at a location downstream of the fan blade leading edges for most or all span positions in an attempt to reduce noise. However, fan blade arrangements that may attempt to mitigate noise may come at the expense of reduced propulsive efficiency.
Prior compressor airfoil geometries may not be suitable for the compressor section of gas turbine engines using a geared architecture, since the significantly different speeds of the compressor changes the desired aerodynamics of the airfoils within the compressor section. Counter-rotating fan and compressor blades, which may be used in geared architecture engines, also present design challenges.